Heretofore, in such as the serger, the double chain stitch sewing machine, or the interlock stitch sewing machine, the gas carrying threading device which is connected by a hollow looper thread guide which leads from a thread introduction portion which inserts the looper thread to a looper thread guide outlet of a loop-taker point of the looper and which feeds a looper thread by utilizing a flow of a pressurized gas which is supplied to the hollow looper thread guide is known.
By this gas carrying threading device, a complicated thread guard is unnecessary and a threading that a handleability is easy can be performed. Therefore, there are no mistake of the threading, no protrusion of the thread in mid-process, and no entanglement of the inserted looper thread with other thread, and thereby the threading can be performed at once by the extremely easy operation.
In a structure of such the gas carrying threading, a pathway for the threading becomes considerably simple, and an operation of the threading becomes easy, and an entanglement of the thread or an incidence of a thread breakage can be dissolved.
However, in the structure of such the gas carrying threading, while pressing a stopper shaft (positioning pin) for a stop positioning plate by one hand, a pulley is rotated manually by the other hand, and thereby a stitch forming device must be locked and concurrently a threading connecting device must be connected. Therefore, it is difficult to understand how to use this threading device for the operator who is not familiar with the sewing machine, and an insertion operation of the thread which is performed by using both hands concurrently is considerably complex, thereby the training of that purpose is necessary.
For this reason, the gas carrying threading device of sewing machine which generates the pressurized gas for carrying the looper thread by gas in the gas supply pump which operates by changing over the sewing machine motor which drives a stitch forming device and is able to perform the threading to the looper by one-touch operation is proposed (refer to Patent document No. 1).